A by-wire type braking device for a motorcycle is known wherein the amount of operation of a brake operating portion such as a brake lever is detected electrically and wheel braking means is operated on the basis of the detected value with use of hydraulic pressure created by a hydraulic modulator. See, for example, JP-A No. 310717/2001.
A by-wire type braking device is known wherein a master cylinder is interlocked with a brake lever (brake operating portion) and a brake caliper (wheel braking means) for imparting a braking force to a wheel by a hydraulic operation that are connected together through a main brake passage provided with a first electromagnetic opening/closing valve of a normally open type. A hydraulic modulator is provided for supplying a hydraulic pressure generated by an electric actuator to the brake caliper that is connected to the main brake passage on the brake caliper side with respect to the first electromagnetic opening/closing valve. A hydraulic loss simulator is provided for exerting a simulative hydraulic reaction force on the master cylinder in accordance with the amount of operation of the brake operating portion and is connected to the main brake passage on the master cylinder side with respect to the first electromagnetic opening/closing valve. A second electromagnetic opening/closing valve of a normally closed type is disposed between the main brake passage and the hydraulic loss simulator.
In this known braking device, when the brake is not actuated, the first electromagnetic opening/closing valve is open and the second electromagnetic opening/closing valve is closed, then when there is a braking input, an electric current is supplied to the first electromagnetic opening/closing valve to close the same valve, thereby closing the main brake passage. Thus, the brake caliper and the hydraulic modulator are disconnected from the master cylinder, and a hydraulic pressure proportional to the amount of operation of the brake lever is generated by the hydraulic modulator and is supplied to the brake caliper to actuate the brake. At the same time, an electric current is supplied to the second electromagnetic opening/closing valve to open the same valve, whereby the hydraulic loss simulator and the master cylinder communicate with each other and a simulative reaction force developed by the hydraulic loss simulator acts on the brake operating portion through the master cylinder.
However, in the braking device of this type, it is possible that there will occur a time lag from the time the amount of operation of the brake operating portion is detected until the hydraulic pressure of the wheel braking means is changed. Consequently, in the case where the time lag increases, the actual amount of operation of the brake operating portion further increases when the hydraulic modulator is controlled on the basis of the amount of operation of the brake operating portion, with a consequently increase in the difference between a target control pressure in the hydraulic modulator and the actual braking pressure in the wheel braking means. Therefore, with respect to the point of feeling of the rider, it is not preferable that the hydraulic modulator be controlled for a sudden increase of its pressure so as to compensate for the aforesaid difference when the control of the hydraulic modulator has proceeded from this state.